CHILE AQUACULTURE SI Productive performance of juvenile Patagonian red octopus (Enteroctopus megalocyathus) fed with fresh preys: are relevant the quantity of protein and energy on diets? Ranferi Guti errez 1,2, *, Iker Uriarte 1,2 , Gabriel Yany 3 & Ana Far  ıas 1,2 1 Hatchery de Invertebrados Marinos, Instituto de Acuicultura, Universidad Austral de Chile, Puerto Montt, Chile 2 Doctoral scholarship of CIEN Austral, CONICYT Regional R10C1002 y Programa de Doctorado en Acuicultura, Pontificia Universidad Cat olica de Valpara  ıso, Valpara  ıso, Chile 3 Escuela de Ciencias del Mar, Facultad de Recursos Naturales, Pontificia Universidad Cat olica de Valpara  ıso, Valpara  ıso, Chile Correspondence: A Far  ıas, Instituto de Acuicultura, Universidad Austral de Chile, P.O Box 1327, Puerto Montt, Chile. E-mail: afarias@spm.uach.cl * Present address: R Guti errez Universidad Aut onoma de Nayarit, Unidad Acad emica de Medicina Veterinaria y Zootecnia carretera a Chapalilla KM 3.5, Compostela, Nayarit, M exico. Abstract This study was conducted to investigate if the pro- ductive performance of Patagonian red octopus (Enteroctopus megalocyathus) is related to the quan- titative contents of protein and energy of fresh diets based in marine preys. Six diets with P/E ratios of 35 (100% crab = C100), 41 (100% fish = F100), 44 (25% squid and 75% fish = S25: F75), 46 (50% squid and 50% fish = S50:F50), 48 (75% squid and 25% fish = S75:F25) and 51 (100% squid = S100) g protein MJ 1 during 83 days were evaluated in octopuses weighing 297  120 g. The growth and body biochemistry of the octopuses were not affected by the diets, however, food and lipid intake were affected, with crab diet obtaining the highest intake in both cases. The higher values of dry matter digestibility were achieved in S100 and S50:F50 diets, the highest protein digestibility was obtained with S100 and C100 diets, while the highest energy digestibility was achieved by diet S75:F25 and F100. Feed efficiency varied between the diets and protein/energy ratio alone explained 82.8% of the total variance. Besides, octopus fed F100 and C100 showed the highest body protein deposition. So, although it had no significant differences in growth and survival between the different diets, the feed efficiency and nitrogen deposition changed in relation with the protein/energy ratio of fresh diets. It is discussed that is possible to maintain growth of octopuses and to improve the feed effi- ciency and protein deposition parameters by opti- mizing the P/E values of diet. Keywords: Enteroctopus megalocyathus, growth performance, protein deposition, protein/energy ratio, octopus nutrition Introduction The Patagonian red octopus Enteroctopus megalocy- athus (Gould) is one of two commercially impor- tant octopus species in southern Chile (Rocha & Vega 2003; Uriarte, Iglesias, Domingues, Rosas, Viana, Navarro, Seixas, Vidal, Ausburger, Pereda, Godoy, Paschke, Far  ıas, Olivares & Zu~ niga 2011). It inhabits the southern tip of South America from latitude 42°S approximately in Chile and Argen- tina, up to the Strait of Magellan that connects © 2014 John Wiley & Sons Ltd 64 Aquaculture Research 2015, 46 (Suppl. 1), 64–75 doi: 10.1111/are.12585